Cold brew is not iced coffee with better marketing. Iced coffee is brewed hot and then chilled or poured over ice, and as it cools its chlorogenic acids break down into quinic and caffeic acids that taste harsh and stale. Cold brew never touches hot water: coarse grounds steep in cool or room-temperature water for 12 to 24 hours, then get filtered through paper, a metal sieve, or felt into a concentrate that is diluted with water or milk and can even be served piping hot without losing its mellow profile. The method traces back to Dutch trading ships in the 1600s, where lighting a fire to boil water was a hazard, and to Japan, where the Dutch technique became known as Dutch coffee and grew into Kyoto-style slow drip towers that pass water through the grounds one drop at a time.

The chemistry is counterintuitive. A 24-hour cold steep ends up with more caffeine by volume than a six-minute brew at 98 degrees Celsius, and cold brew’s pH is nearly the same as hot coffee. Its smoothness comes from lower titratable acidity, because large bitter acid molecules stay locked in the discarded grounds. The 2010s added nitrogen: a draft coffee predecessor at the Queen’s Kickshaw in New York in 2011, then Stumptown in Portland and Cuvée Coffee in Austin, which poured nitro cold brew on tap at the Slow Food Quiz Bowl on August 14, 2012, and later worked with the Ball Corporation on a widget can.

• Nitrogen barely dissolves in liquid, so it forms microscopic bubbles that stay suspended, the same principle behind stouts like Guinness.
• A restrictor plate in the tap forces coffee through tiny holes to create the cascading pour.
• Nitro is served without ice because ice cubes act as nucleation sites that knock the gas out and flatten the foam.
• Starbucks launched Nitro Cold Brew in 500 stores in summer 2016 and offered it at more than half its US locations by 2020.
• Wholesaler Rise Brewing Co. was filling up to 1,500 kegs a day of nitro cold brew for offices and restaurants.